The oil recovery processes are known as primary, secondary and tertiary or enhanced recovery processes.
The primary recovery of oil takes place when the fluids flow toward the wells is the result of the natural energy present in the reservoir.
The secondary recovery takes place when energy is added to the reservoir by the injection of an immiscible fluid, keeping or restarting the displacement of oil toward the well production.
The enhanced or tertiary recovery of oil, “Enhanced Oil Recovery” (EOR), is the application of processes that produce an additional oil recovery, where the injection of a fluid into the reservoir modifies the original characteristics of the rock and/or the fluids involved in the displacement by reducing the oil viscosity, modifying the behavior of the phases, reducing the interface tension, etc.
Among the EOR processes, the microbial recovery of hydrocarbons is found, “Microbial Enhanced Oil Recovery” (MEOR), which can be put into practice by three strategies:                1) Inducing selectively the growth and metabolic activity of indigenous microorganisms present in the reservoirs, through the injection of nutrients and carbon sources that favor the microbial activity to produce metabolites such as CO2, CH4, solvents, acids and tensoactive biomolecules (biosurfactants), that are useful for the mobilization, and therefore, the oil recovery from the reservoirs.        2) Adding exogenous microorganisms capable of producing useful metabolites for the recovery of oil.        3) Applying bioproducts such as tensoactive biomolecules, enzymes, acids, biopolymers among others, that improve the reservoir conditions and favor the release of oil.        
Most patents on microbial enhanced oil recovery imply the injection of microorganisms or the selective stimulation of reservoir indigenous microorganisms. The aim is to make the microorganisms grow to produce compounds such as gases, biosurfactants or solvents, that modify the properties of the oil and allow its mobilization. These compounds are produced in situ and depend on suitable environmental and nutritional conditions for the development of such microorganisms.
On the other hand, many of the strains that produce tensoactive biomolecules require aerobic conditions for their growth. However, most of these microorganisms cannot withstand both high temperatures and salt concentrations.
In the patent application WO2009009382 “Process for enhanced oil recovery using a microbial consortium”, published on Jan. 15, 2009, a process for the selection and enrichment of microorganisms, where the nutritional components to propagate the microbial growth is defined. The culture medium and microorganisms were injected into the well, which was closed up to 3 weeks to allow the development of the microorganisms, the production of metabolites and the oil recovery.
In the patent application US 2009/0029879 A1 “Process for enhanced oil recovery using a microbial consortium”, published on Jan. 29, 2009, Soni et al. describe a microbial consortium that was injected along with a culture medium designed for its growth. The metabolic products increased the oil recovery. The consortium was able to grow a temperature of 67° C.
Tensoactive biomolecules are a heterogeneous group of amphiphilic compounds with tensoactive properties. These compounds feature a variety of chemical structures and many of them are produced by microorganisms.
Tensoactive biomolecules have high surface activity and are stable within a wide interval of temperatures, pH and salinity, in addition to be biodegradable and less toxic than chemical surfactants. These biomolecules reduce the surface tension (ST) and the interfacial tension (IFT), easing the formation of emulsions. Some of their potential applications include the improvement of the mobility of oils, the enhanced oil recovery by microorganism (MEOR) and the hydrocarbons biodegradation by increasing the bioavailability of hydrophobic compounds.
These compounds can improve some properties of oils, such as the decrease of the surface and interfacial tensions and the reduction of oil viscosity to make it more fluid. Among patent documents on tensoactive biomolecules applied in EOR, the following are found:
The patent U.S. Pat. No. 4,522,261 “Biosurfactant and enhanced oil recovery”, from Jun. 11, 1985, where McInerney et al. propose a process for increasing the oil recovery from reservoirs by a pure culture of Bacillus licheniformis and the lichenysin surfactant that is produced. The obtained results and the claimed subject are based on oil recovery experiments performed in glass column systems, packed with quartz sand impregnated with crude oil. The characteristics of the employed oil are not stated; the columns were kept at 25° C., under different conditions from those in the reservoir and with only qualitative oil recovery results. The characteristics and culture conditions of the microorganism B. licheniformis are very different from those used with the microorganism Serratia marcescens SmSA featured in the present invention.
Hames et al. (2015: Patents on biosurfactants and future trends. Chapter 11. In: BIOSURFACTANTS Production and Utilization-Processes, Technologies, and
Economics, Edited by Kosaric N. and Sukan F. V., CRC Press Taylor & Francis Group, Boca Raton London New York, FL. 165-225) present a wide review of patents on the production of biosurfactants and their application, including the recovery of reservoir oils. This review covered up to 2013 and the authors show that the main microorganisms that produce biosurfactants belong mainly to: Acinetobacter, Bacillus, Pseudomonas, Torulopsis and Candida genus. Among the patents reviewed in this study regarding the use of Serratia marcescens, none considered neither its application in the production of biomolecules with tensoactive activity nor its use in some biotechnological process for oil recovery.
In “novel sucrose lipid produced by Serratia marcescens and its application in enhanced oil recovery”, Journal of Surfactants and Detergents, Vol. 3, No. 4 (October 2000), pp. 533-537, Vikas Pruthi and Swaranjit S. Cameotra reported that Serratia marcesens cultivated in a medium with sucrose at 2% (p/v) produced a saccharolipid with emulsifying properties. With this compound, recovery tests were carried out, employing glass columns, packed with sand saturated with oil; the results were 78% of crude oil recovery and 90% of kerosene. The conditions (temperature and oil type) under which the experiment was carried out are not stated.
Roldan et al. in “Evaluation of the effect of nutrient ratios on biosurfactant production by Serratia marcescens using a Box-Behnken design”, Colloids and Surfaces B: Biointerfaces 86 (2011), pp. 384-389, study the microorganism Serratia marcescens and the effect of the C/N, C/Fe and C/Mg ratios on the production of biosurfactants using glucose as carbon source by a Box-Behnken experiment design. With the best treatment, a yield of 4.1 g/L of biosurfactant was obtained, which diminished the surface tension to 31 mN/m and produced maximum oil spreading of 1.1 cm.
Ibrahim et al. in “Production and partial characterization of biosurfactant produced by crude oil degrading bacteria”, International Biodeterioration & Biodegradation 81 (2013), pp. 28-34, report the isolation of several biosurfactant producer microorganisms using a mineral medium, where the substrate was crude oil. Among the evaluated microorganisms, Serratia marcescens and its produced biosurfactant were reported. The biosurfactant was used for oil recovery experiments in packed columns. With these experiments, 30% oil recovery was obtained by waterflooding and 46% by the biosurfactant action, with a total oil recovery of 76%. The authors do not mention the conditions under which the column recovery experiment was carried out, the type of rock, the oil characteristics and temperature.
In the previous references, the recovery of oil by tensoactive biomolecules were performed in columns packed with siliciclastic rocks, which are porous media with high permeability. In addition, these reports lack of fundamental information for the studies on the oil recovery such as pressure, temperature, API gravity and oil viscosity.